Start and stop switch actuating pushbuttons interlocked with a door



R. A. roan START AND STOP SWITCH AC STNER BUTTONS Feb. 17, 1970TUATING'PUSH INTERLOCK ED--WITH A DOOR Filed Sept 17, 1968 FIG 3INVENTOR. RICHARD A. FOERSTNER BY ATTORNEY United States Patent US. Cl.200-50 2 Claims ABSTRACT OF THE DISCLOSURE A mechanical switcharrangement for a microwave oven which assures that the unit will beswitched off any time the door is opened or the proper button is pushed,and will not be turned on again until the user closes the door andpushes a second button to start the unit.

Background of the invention In recent times, there have appeared on themarket for use by the avarage housewife, ovens for preparing food by theuse of short electrical magnetic waves or microwaves which aretransmitted into the oven chamber from a wave generator. In thesemicrowave ovens, it is essential that the generator be off whenever theoven door is opened. It is also desirable that the unit not be operatedwithout some food in the oven since this type of operation tends to beharmful to the wave generator. Thus, the unit must be designed so thatthe generator is turned off the instant the door is opened, but will notstart when the door is closed unless the user again wishes to start theunit. In the past, control of the starting and stopping of the unit hasbeen achieved by a control circuit including an electrical relay and asafey interlock switch in-the door hinge linkage. However, in the eventof failure of the relay for any reason, the stop-start function of thecontrol system would thereby be inoperative. Thus, while the unit wouldalways shut off when the door is opened, owing to the additional safetyinterlock switch, yet, depending upon in which position the relayfailed, the unit could either not be turned on or not be turned off whenthe door is closed.

SUMMARY OF THE INVENTION My invention provides a mechanical arrangementwhich will positively operate each time the oven door is opened to stopoperation of the wave generator. The mechanical arrangement is such thateven though the oven door is subsequently closed, the unit will notcommence operation unless the operator depresses a start button. Themechanical arrangement is very simple, completely foolproof and thusprovides an entirely reliable arrangement for shutting off the wavegenerator the instant the oven door is opened. The arrangement,therefore, makes the use of a microwave oven completely safe by even themost inexperienced operator. The arrangement is so simple it can beincorporated into a microwave oven unit without adversely affecting thecost of the unit, and the arrangement does not detract from theaesthetics of the final finished unit since it is completely hiddenwithin the control panel provided for the unit.

Brief description of the drawings FIGURE 1 is a perspective view of amechanical interlocking arrangement incorporating the principles of myinvention, the view being from the inside of the control panel portionof the unit looking outwardly and showing the unit with the door closedand the start button depressed;

FIGURE 2 is a perspective view similar to FIGURE 1, but showing the ovendoor opened; and

FIGURE 3 is a view similar to FIGURE 1 and showing the oven door closedbut with the start button not depressed.

Description of the preferred embodiment The reference numeral 10designates a side wall of the oven chamber, which side wall 10 would bethe right interior side wall when the unit is viewed while facing it.Side wall 10 is joined to a recessed portion 12 of the front wall 16 ofthe unit into which recessed portion 12 the oven door 14 fits so thatthe door is flush with the front wall 16. The front wall 16 is thenjoined with an exterior side wall 18, which would be the right side wallwhen viewed as facing the unit. The space between the oven side wall 10and the exterior side wall 18 provides an area for location of thecontrols for the unit. The front wall 16 thus is the face of the controlpanel, and protruding from the front wall or face 16 are two controlbuttons, a start button 20 and a stop button 22.

Included within the space between oven side wall 10 and the exteriorside wall 18 is a switch 24 having an operating lever 26. The switch 24is one of the main switches which operates the wave generator (notshown) that produces the microwaves which heat the food or other objectsplaced inside the oven. As is well known to those skilled in the art,microwave ovens are commonly equipped with a second safety switch (notshown) operatively associated with the oven door hinge so that theswitch will be open the instant the oven door is opened, and will beclosed when the door is closed. This second safety switch is in serieswith switch 24 in the control circuit so that both switches must beclosed before the wave generator will be turned on. The operating lever26 for switch 24 is preferably constructed of a resilient material sothat it at all times is biased away from the switch 24. By any suitableinternal connection, the switch 24 will be closed whenever the operatinglever 26 is forced toward the switch 24, and the switch 24 will be openwhen the operating lever 26 is allowed to move away from the switch 24.This could be done, for example, by a small button 28 extending from theswitch 24 which button will be depressed when the operating lever 26 ismoved toward the switch to close the switch and thus turn the unit on.The operating lever 26 is at all times engaged with a cam 30 which isafiixed to the lower end of a rod 32 the upper end of which is connectedto the double cam 34. As shown, the start button 20 and stop button 22are in side-by-side spaced-apart position and each of them extendsinwardly to the space behind the front wall 16. The rod 32 extendsupwardly between the inner ends of the start button 20 and stop button22, and the double cam 34 has one end extending into recess 36 formed inthe inner end of start button 20 while the other end of double cam 34extends into a similar recess 38 in the stop button 22. It should benoted that for ease of manufacture and reduced cost, the start button 20and stop button 22 are identical.

In FIGURE 1, the operative components are shown in the relativepositions necessary for the unit to operate. Thus, the oven door 14 isin a closed position, the start button 20 is depressed and the switch 24is, therefore, closed. The closing of the switch 24 is accomplishedthrough the cam arrangement when the start button 20 is depressedinwardly. When the start button 20 is depressed inwardly, theend of thedouble cam 34 engaged in recess 36 will be moved so as to rotate theoperating rod 32 in the direction of the arrow in FIGURE 1. This in turnrotates the cam 30 so as to move the operating lever 26 toward theswitch 24 depressing the button 28 to close the switch 24. Thus, thewave generator will be turned on and the unit placed in operation if thesecond safety switch associated with the oven door is also closed tocomplete the control circuit.

In order to reset the start button 20 and thus open switch 24 wheneverthe oven door 14 is opened, a reset arm 40 is provided. The arm 40 ismade of a resilient material and has its upper end 42 afiixed to theback side of the recessed portion 12 of the front wall. The transverselyextending leg 44 of the arm 40 extends behind the start button 20 and inits path. As previously mentioned, the reset arm 40 is constructed of aresilient material so that the leg 44 is biased toward the front wall16. Secured to the leg 44 of the reset arm 40 in any suitable manner isan operating button 46. Button 46 extends through an opening in therecessed portion 12 of front wall 16 and extends slightly beyond theportion 12 so as to be engageable with the inside of the oven door 14when that door is closed. As shown in FIGURE 1, when the oven door 14 isclosed, the operating button 46 will be engaged by the door 14 and willbe pushed inwardly carrying with it the leg 44 of the reset arm 40. Theleg 44 will be forced inwardly a sufiicient amount to permit the startbutton 20 to be depressed thus closing the switch 24 as previouslydescribed.

If the oven door 14 is opened, however, the arrangement resets the startbutton 20 and opens the switch 24. This is illustrated in FIGURE 2 inwhich the oven door 14 is shown in an opened position and thus thebutton 46 protrudes outwardly from the recessed portion 12 of front wall16. The reset arm 40 thus is biased forwardly and the leg 44 extendsbehind and engages the rear of the start button 20, forcing it outwardlyand through the cam arrangement opening switch 24. If an attempt is madeto depress start button 20 with door 14 open, it can be moved inwardlyagainst the resistance of arm 40 and will close switch 24, but thepreviously mentioned second safety switch will prevent the Wavegenerator from starting unless the door 14 is also closed. Of course,when the start button 20 is released, and if the door 14 is open, thearm 40 will reset the start button 20 and open switch 24. However, oncethe oven door 14 is closed, the small operating button 46 will be forcedinwardly moving the leg 44 of the reset arm 40 inwardly as shown inFIGURE 3. In this position, there is suflicient space between the rearof the start button 20 and the leg 44 so that the start button 20 can bedepressed and will remain in the start position when released.

In the event that it is desirable at any time to shut the tmit off eventhough the oven door 14 remains closed, the operator can depress thestop button 22. If the unit is in operation, the start button 20 will,of course, be in the position shown in FIGURE 1. In this position, thestop button 22 is extended outwardly from the front wall 16, and whenthe stop button 22 is pressed inwardly, the double cam 34 will berotated in a direction opposite the arrow of FIGURE 1. When thisrotation of the double cam 34 occurs, it will force the start buttonoutwardly to off position, and at the same time through the rod 32 thecam 30 will be rotated allowing the operating lever 26 to move away fromthe switch 24 thereby opening the switch and shutting off the unit.Because the earns 30 and 34 rotate about a fixed axis, it should benoted that the stop button 22 will be forced outwardly beyond its original position at the time that the start button 20 is depressed to turnthe unit on. When the stop button 22 is then depressed back to itsoriginal position, it will return the start button 20 also to itsoriginal position as shown in FIGURE 3. Thus, merely returning the stopbutton 22 to its original position will shut the unit off and return thestart button 20 also to its original position and in order to start theunit again, the start button 20 will again have to be pressed inwardly.

In the above description, it will be evident that I have provided a verysimple mechanical arrangement for use in apparatus, such as ovens, whereit is desired to assure that the door is closed before the oven can bestarted. This is done in my invention in a simple but positive manner.The mechanical arrangement is foolproof and easily operated by even theuninformed operator. It will be evident to those skilled in the art thatvarious revisions and modifications can be made to the arrangementdescribed herein without departing from the spirit and scope of theinvention. It is my intention, however, that any such revisions ormodifications which are obvious to those skilled in the art will beincluded within the scope of the following claims.

I claim:

1. In a microwave oven or the like having a normally closed door and amain electrical switch for controlling operation of said oven, saidswitch having switch operating means operatively combined therewith toopen and close said switch, the improvement in combination therewith ofa safety switching arrangement, said arrangement comprising: a pair ofmovable stop and start buttons positioned adjacent each other; a firstrotatably mounted cam having portions engageable with both of saidbuttons so that when one of said buttons is moved to an operativeposition the other is moved to an inoperative position by rotation ofsaid first cam; a second rotatably mounted cam operatively connected tosaid first cam by a rotatable member rotatable with said first andsecond cams, said switch operating means being operatively engaged withsaid second cam to close said switch as said cam rotates when said startbutton is moved to its operative position and to open said switch assaid cam rotates when said stop button is moved to its operativeposition; and reset means operatively combined with said door and saidstart button so that when said door is opened said start button is movedto its inoperative position, said reset means including a reset arm, aportion thereof normally extending into the path of movement of saidstart button defined when said button is moved from its inoperative toits operative position, and door engaging means operatively combinedwith said arm and engagea'ble by said door when closed to move said armout of said path of said start button.

2. The combination of claim 1 in which said start and stop buttons arelocated side-by-side and each has a recess into which extends a portionof said first cam, the pivotal axis of said first cam being locatedbetween said buttons.

References Cited UNITED STATES PATENTS 1,619,134 3/1927 Kern 200-6l.792,312,243 2/1943 Evans et a1. ZOO-61.76 X 2,568,002 9/1951 Hart et a1.2,737,262 3/ 6 Ferraris. 3,210,490 10/1965 Yake. 3,229,061 1/ 1966Harrofi ZOO-61.62

FOREIGN PATENTS 957,794 2/1950 France. 508,178 1/ 1928 Germany.1,084,347 6/1960 Germany.

576,165 4/1958 Italy.

ROBERT K. SCHAEFER, Primary Examiner R. A. VANDERHYE, Assistant ExaminerUS. Cl. X.R. 200-5, 61.62, 159

